You should know about scrap metal pricing and global commodities market.
You should understand dead metric ton vs real tonnage.
It's important to know about the composite materials of a ship, especially the boilers, turbines, fittings/trimmings - what can be salvages and resold and what can be scrapped.
Are their toxic materials on board the ship?
Towing distance - who pays.
Bank loans/financing - how is it structured.
There are hundreds of questions you can ask but the best is to work as a volunteer at a ship scrapyard.